Amenorrhea (uh-men-o-REE-uh) is the absence of menstruation — one or more missed menstrual periods. Women who have missed at least three menstrual periods in a row have amenorrhea, as do girls who haven't begun menstruation by age 15.

The most common cause of amenorrhea is pregnancy. Other causes of amenorrhea include problems with the reproductive organs or with the glands that help regulate hormone levels. Treatment of the underlying condition often resolves amenorrhea.

The main sign of amenorrhea is the absence of menstrual periods. Depending on the cause of amenorrhea, you might experience other signs or symptoms along with the absence of periods, such as:

Milky nipple discharge

Hair loss

Headache

Vision changes

Excess facial hair

Pelvic pain

Acne

When to see a doctor

Consult your doctor if you've missed at least three menstrual periods in a row, or if you've never had a menstrual period and you're age 15 or older.

Amenorrhea can occur for a variety of reasons. Some are normal during the course of a woman's life, while others may be a side effect of medication or a sign of a medical problem.

Natural amenorrhea

During the normal course of your life, you may experience amenorrhea for natural reasons, such as:

Pregnancy

Breast-feeding

Menopause

Contraceptives

Some women who take birth control pills may not have periods. Even after stopping oral contraceptives, it may take some time before regular ovulation and menstruation return. Contraceptives that are injected or implanted also may cause amenorrhea, as can some types of intrauterine devices.

Medications

Certain medications can cause menstrual periods to stop, including some types of:

Antipsychotics

Cancer chemotherapy

Antidepressants

Blood pressure drugs

Allergy medications

Lifestyle factors

Sometimes lifestyle factors contribute to amenorrhea, for instance:

Low body weight. Excessively low body weight — about 10 percent under normal weight — interrupts many hormonal functions in your body, potentially halting ovulation. Women who have an eating disorder, such as anorexia or bulimia, often stop having periods because of these abnormal hormonal changes.

Excessive exercise. Women who participate in activities that require rigorous training, such as ballet, may find their menstrual cycles interrupted. Several factors combine to contribute to the loss of periods in athletes, including low body fat, stress and high energy expenditure.

Stress. Mental stress can temporarily alter the functioning of your hypothalamus — an area of your brain that controls the hormones that regulate your menstrual cycle. Ovulation and menstruation may stop as a result. Regular menstrual periods usually resume after your stress decreases.

Hormonal imbalance

Many types of medical problems can cause hormonal imbalance, including:

Polycystic ovary syndrome (PCOS). PCOS causes relatively high and sustained levels of hormones, rather than the fluctuating levels seen in the normal menstrual cycle.

Pituitary tumor. A noncancerous (benign) tumor in your pituitary gland can interfere with the hormonal regulation of menstruation.

Premature menopause. Menopause usually begins around age 50. But, for some women, the ovarian supply of eggs diminishes before age 40, and menstruation stops.

Structural problems

Problems with the sexual organs themselves also can cause amenorrhea. Examples include:

Uterine scarring. Asherman's syndrome, a condition in which scar tissue builds up in the lining of the uterus, can sometimes occur after a dilation and curettage (D&C), cesarean section or treatment for uterine fibroids. Uterine scarring prevents the normal buildup and shedding of the uterine lining.

Lack of reproductive organs. Sometimes problems arise during fetal development that lead to a girl being born without some major part of her reproductive system, such as her uterus, cervix or vagina. Because her reproductive system didn't develop normally, she can't have menstrual cycles.

Structural abnormality of the vagina. An obstruction of the vagina may prevent visible menstrual bleeding. A membrane or wall may be present in the vagina that blocks the outflow of blood from the uterus and cervix.

Factors that may increase your risk of amenorrhea may include:

Family history. If other women in your family have experienced amenorrhea, you may have inherited a predisposition for the problem.

Eating disorders. If you have an eating disorder, such as anorexia or bulimia, you are at higher risk of developing amenorrhea.

Infertility. If you don't ovulate and have menstrual periods, you can't become pregnant.

Osteoporosis. If your amenorrhea is caused by low estrogen levels, you may also be at risk of osteoporosis — a weakening of your bones.

Your first appointment will likely be with your primary care physician or gynecologist.

Here's some information to help you prepare for your appointment and know what to expect from your doctor.

What you can do

To get ready for your appointment:

Write down details about your symptoms, including when they started and the date and duration of your last period, if you know when your last period was.

Make note of key medical information, including other conditions for which you're being treated and the names and dosages of any medications, vitamins or supplements you regularly take.

Review your family history, checking to see whether your mother or any sisters have also had menstrual problems.

Write down questions to ask your doctor, listing the most important ones first in case time runs short.

For amenorrhea, some basic questions to ask your doctor include:

What might be causing me to miss my periods?

Do I need any tests? How should I prepare for those tests?

What treatments are available? Which do you recommend for me?

Do you have any informational brochures on this topic? What websites do you recommend?

What to expect from your doctor

Your doctor will likely ask you a number of questions, such as:

When was your last period?

Are you sexually active?

Could you be pregnant?

Do you use birth control?

Are you under any stress?

Have you experienced unexplained weight gain or weight loss?

How often and how intensely do you exercise?

Do you have any other medical conditions?

During your appointment, your doctor will perform a pelvic exam to check for any problems with your reproductive organs. If you've never had a period, your doctor may examine your breasts and genitals to see if you're experiencing the normal changes of puberty.

Amenorrhea can be a sign of a complex set of hormonal problems. Finding the underlying cause can take time and may require more than one kind of testing.

Lab tests

A variety of blood tests may be necessary, including:

Pregnancy test. This will probably be the first test your doctor suggests, to rule out or confirm a possible pregnancy.

Thyroid function test. Measuring the amount of thyroid-stimulating hormone (TSH) in your blood can determine if your thyroid is working properly.

Ovary function test. Measuring the amount of follicle-stimulating hormone (FSH) in your blood can determine if your ovaries are working properly.

Prolactin test. Low levels of the hormone prolactin may be a sign of a pituitary gland tumor.

Hormone challenge test

For this test, you take a hormonal medication for seven to 10 days to trigger menstrual bleeding. Results from this test can tell your doctor whether your periods have stopped due to a lack of estrogen.

Imaging tests

Depending on your signs and symptoms — and the result of any blood tests you've had — your doctor might recommend one or more imaging tests, including:

Ultrasound. This test uses sound waves to produce images of internal organs. If you have never had a period, your doctor may suggest an ultrasound test to check for any abnormalities in your reproductive organs.

Magnetic resonance imaging (MRI). MRI uses radio waves with a strong magnetic field to produce exceptionally detailed images of soft tissues within the body. Your doctor may order an MRI to check for a pituitary tumor.

Scope tests

If other testing reveals no specific cause, your doctor may recommend a hysteroscopy — a test in which a thin, lighted camera is passed through your vagina and cervix to look at the inside of your uterus.

Treatment depends on the underlying cause of your amenorrhea. In some cases, contraceptive pills or other hormone therapies can restart your menstrual cycles. Amenorrhea caused by thyroid or pituitary disorders may be treated with medications. If a tumor or structural blockage is causing the problem, surgery may be necessary.

Some lifestyle factors — such as too much exercise or too little food — can cause amenorrhea, so strive for balance in work, recreation and rest. Assess areas of stress and conflict in your life. If you can't decrease stress on your own, ask for help from family, friends or your doctor.

Be aware of changes in your menstrual cycle and check with your doctor if you have concerns. Keep a record of when your periods occur. Note the date your period starts, how long it lasts and any troublesome symptoms you experience.

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